Forces on Moving Charges in a Magnetic Field

A current is the result of the motion of charged particles, and a wire carrying a current can experience a force in a magnetic field.

If the force were exerted directly on the charge carriers, even a beam of charge from a charge gun would experience a force due to a magnetic field.

To find the force caused by a magnetic field on a single charge carrier moving in a wire, we must divide the total force on a length L of wire by the number of charge carriers in this length.

If the wire has a cross sectional area A, and there are nu charge carriers per unit volume, the number of charge carriers in length L is nuAL.

Force per charge = force on wire = BfÎ IL = BfÎI number of carriers nuAL nuA

The number...